Optical auxiliary system for a camera

ABSTRACT

What is described here is an optical auxiliary system for a camera, which is arranged between a recording lens and a camera body and which comprises a relay system for projecting the image of the recording lens onto the film or the video pick-up.  
     The invention is characterised by the provision that the relay system is so structured that it produces more than one image and that the lens disposed directly on the camera body is a zoom lens.

[0001] This is a continuation of pending International ApplcationPCT/DE99/01785 filed Jun. 17, 1999, which designates the United States.

DESCRIPTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an optical auxiliary system fora camera in accordance with the introductory clause of Patent claim 1.

[0004] The camera may be a photographic device, a film camera,particularly for professional applications, or a video camera.

[0005] 2. Prior Art

[0006] An optical auxiliary system, which was taken as the basis whenthe introductory clause was worded, is known from the European PatentEP-A-0 690 327. Other auxiliary systems of the claimed general type areknown from the U.S. Pat. Nos. 5,469,236 or 4,867,549. For an explanationof all the features which are not described here in details explicitreference is made to these prior art references.

[0007] All the known optical auxiliary systems have the feature incommon that the normal recording lens, which is “directly on the camerabody in all other cases”, is attached to the auxiliary system sothat—depending on the configuration of the auxiliary system—it will bespaced from the camera body by a more or less wide distance. As aresult, the operation is rendered more difficult for the operator,particularly when the recording lens is a zoom lens, because theoperator must handle the lens for adjusting the focal length and actuatevarious elements for operating the camera, both over a comparativelylong distance.

[0008] The known systems involve the further disadvantage that theycannot be adapted to different tasks in a simple manner. For instance,it is not possible to use one and the same system as a “straight” systemand after simple retrofitting as a “bent” system.

BRIEF DESCRIPTION OF THE INVENTION

[0009] The present invention is based on the problem of improving anoptical auxiliary system for a camera in accordance with theintroductory clause of Patent claim 1 in such a way that handling willbe facilitated and that the system can be retrofitted for differentapplications in a simple manner.

[0010] One inventive solution to this problem is defined in Patent claim1. Improvements of the invention are the subject matters of claims 2 etseq.

[0011] In accordance with the invention the relay system is sostructured that it produces more than one image and that the lensdisposed on the camera body directly is a zoom lens.

[0012] As a result it is not only possible to realise focusing and apossible rotation of the image “close to the camera” but also to selectthe section or window of the image. In particular, the zoom lens may bea varifocal lens, i.e. a lens in which focussing is not varied when thefocal length is changed.

[0013] On account of this configuration it is moreover possible toretrofit the optical auxiliary system in a comparatively simple manner.It is possible, in particular, to select the object distance between theimage of the recording lens and the first image at a distance so widethat it is possible to insert further systems such as path-folding unitsinto this range.

[0014] It is particularly preferable that the path-folding unit isdisposed between the recording lens and the relay system because in sucha case the optical system, which is arranged in the recording path aheadof the path-folding unit is comparatively small and hence of lightweight.

[0015] In another embodiment the path-folding unit comprises twoelements whereof at least one deflects the light path by 90°. With thisembodiment in particular an “offset” of the optical axis is possiblewhich is suitable to solve also complex recording situations such asthose occurring in macro pictures by means of the inventive auxiliarysystem. It is furthermore possible to achieve an amplification of thedepth of focus.

[0016] In particular, the aforementioned one element may be afront-surface reflector whilst the other element is a path-foldingelement with image inversion so that a non-reversed image is obtained inan intermediate frame.

[0017] The aforedescribed configuration does not only permit an offsetof the optical axis but also the pivoting of the offset optical axis. Tothis end an element is pivotable together with the recording lens insuch a way that the respective pivoting angle of the recording lenscorresponds to twice the pivoting angle of the pivotable element. Thepivotable element may be the front-surface reflector in particular inthis configuration.

[0018] In a preferred embodiment the relay system comprises three lensesand the zoom lens, with a prism for image rotation being disposedbetween the first and the second lens in particular. The two lenseswhich are arranged between the prism for image rotation and the zoomlens present preferably the same design and are disposed in symmetryrelative to the centre plane therebetween.

BRIEF DESCRIPTION OF THE DRAWING

[0019] The present invention will be described in the following byexemplary embodiments, without any restriction of the general inventiveidea, with reference to the drawing to which explicit reference is made,by the way, with respect to the disclosure of all the inventive detailswhich are not disclosed more exhaustively in the text. In the drawing:

[0020]FIG. 1 shows the fundamental structure of a first embodiment;

[0021]FIG. 2 is a view of a second embodiment which involves amodification of the embodiment according to FIG. 1, including an offsetof the optical axis of the recording lens and the relay system;

[0022]FIG. 3 illustrates the structure of a roof prism employed in theinvention;

[0023]FIGS. 4 and 5 are illustrations explaining the increase of thedepth of focus in a modification of the second embodiment, and

[0024]FIG. 6 shows an embodiment of the gearing employed for acompensation of the image position.

DESCRIPTION OF EMBODIMENTS

[0025]FIG. 1 shows a first embodiment of the invention wherein the relaysystem is so structured that it provides more than one intermediateimage.

[0026] To this end, optical relay means 3, 4 and 6 as well as an opticalzoom means 7 are arranged between an optical recording system 1 and animage plane 8 in which a film or a video pick-up may be provided. Theoptical recording system 1 creates an image in a first intermediateimage plane 2. This image is projected into the second intermediateimage plane 5 by the first relay system, which consists of the opticalrelay means 3 and 4 that constitute a tandem system.

[0027] The image created in the image plane 5 is projected into the filmor video pick-up plane 8, respectively, by the second relay system,which consists of the optical relay means 6 with invariable focal lengthand the zoom lens 7. The zoom lens permits here an adjustment of theimage section without the operator being bound to operate a recordinglens, which is far remote due to the relay system.

[0028] The zoom lens 7 may be configured particularly in such a way thatthe image is enlarged or reduced in dependence on the focal length ofthe zoom lens 7.

[0029]FIG. 2 shows a second embodiment wherein elements identical withthose of FIG. 1 are identified by the same reference numerals so that arepeated discussion thereof may be dispensed with.

[0030] In this embodiment elements are provided between the firstintermediate image plane 2 and the first relay system, which consists ofthe optical relay means 3 and 4, which elements offset an optical axis 9of the optical recording system 1 from a common optical axis 10 sharedby the optical means 3, 4, 6 and 7.

[0031] The elements deflecting the path of rays are a front-surfacereflector 11 and a roof prism 13 with image inversion. One embodiment ofthe roof prism 13 is illustrated in FIG. 3 which is referred toexplicitly for an explanation of all the details.

[0032] In the embodiment shown in FIG. 2 it is possible to pivot thelens 1 about an axis 12 orthogonal on the drawing plane. To this end,the front-surface reflector 11 is rotatable about the axis 12. Theoptical recording system 1 is here pivotable together with thefront-surface reflector 11 in such a way that the respective pivotingangle of the optical recording system 1 is twice the angle of rotationof the front-surface reflector 11 about the axis 12.

[0033] It is furthermore possible - in a manner known per se—to pivotthe lens 1 about the section of the optical axis between the elements 11and 13. It is also possible to perform a rotation about the optical axis10, equally in a manner known per se.

[0034] When the lens 1 is pivoted about the section of the optical axisbetween the elements 11 and 13 the image on the image plane 8 wouldrotate without compensation. Therefore a prism 14 for image rotation isarranged between the optical relay means 3 and 4. The function of thisprism will be explained in more details in the following with referenceto FIG. 6.

[0035] The front-surface reflector 11 may be used not only forperforming a pivoting motion of the recording lens 1 but also for thepurpose of sharply projecting an object plane on the image plane 8,which defines an angle different from 90° relative to the optical axis.This will be explained below with reference to the FIGS. 4 and 5.

[0036]FIG. 4 is a schematic view of a section from a modification of thesecond embodiment. Here elements identical with those illustrated inFIG. 2 are identified by the same reference numerals so that a repeateddiscussion may be dispensed with here. With the normal position of thefront-surface reflector 11, the recording lens 1 creates a sharp imageof the object plane B, which is orthogonal on the optical axis 9, in theimage plane B′. The intermediate image B′ is projected into the secondintermediate image plane B″ by the relay lens 3. As a result the opticalpath is deflected by the elements 11 and 13—as has been explained abovewith reference to FIG. 2.

[0037] When the object a-b to be recorded is located in the plane B_(s),which is “oblique” relative to the optical axis 9, rather than in theorthogonal plane, an image of this object is produced in the equally“oblique” planes B_(s)′ or B_(s)″, with the normal position of thefront-surface reflector 11, so that it cannot be sharply focussed intothe image plane 8.

[0038] In accordance with the present invention the front-surfacereflector 11 is now (also) rotatable independently of the recording lens1. When the angular position of the reflector 11 is varied from thevalue x1 as indicated in FIG. 4 to the value x2 (FIG. 5) the planeB_(s)′ is projected onto the plane B″ orthogonal to the optical axis,due to the pivoting angle x3. As a result it is possible to focus aplane inclined relative to the optical axis sharply on the image plane.

[0039] As has already been mentioned, FIG. 6 illustrates an embodimentfor the compensation of the image position, as provided by the presentinvention. Elements identical with those shown in the previouslydiscussed figures are again identified by the same reference numerals sothat a repeated description may be dispensed with. A bevel crown gear16, which is connected to a pivoting head 15, drives the conical gearwheel 17 when the head is pivoted. This conical gear wheel is fixedlyconnected to a gear 18, which drives the tube 20 via the gearing 19. Theprism 14, which is a Pechan-type prism in the illustrated embodiment, isrotated via the differential gear, the gearing 21, the conical gearwheel 22 and the bevel crown gear 23, at half the pivoting rate relativeto the rotating speed of the pivoting head 15. Hence the image is notrotated on the plane 5.

[0040] It is possible to employ any other gearing instead of the gearset illustrated here, provided that this gearing has a gear transmissionratio correspond to that of the respective prism used. The gear setshown here is, however, particularly space-saving.

1. Optical auxiliary system for a camera, which is inserted between arecording objective (1) and a camera body and which comprises a relaysystem consisting of the three lenses (3, 4, 6) and the zoom lens (7)for projecting the image from the recording lens onto the film (8) orthe video pick-up, characterised in that the lenses of said relay system(3, 4, 6 and 7) are so structured that they produce more than one image,with the object being projected into a second intermediate image plane(5 or B″), and that the lens disposed directly on said camera body is azoom lens (7).
 2. Optical auxiliary system according to claim 1 ,characterised in that a path-folding unit (11, 13) is disposed betweensaid recording lens (1) and said relay system (3, 4, 6 and 7). 3.Optical auxiliary system according to claim 2 , characterised in thatsaid path-folding unit (11, 13) comprises two elements whereof at leastone deflects the light path by 90°.
 4. Optical auxiliary systemaccording to claim 3 , characterised in that said one element is afront-surface reflector (11) while the other element is a path-foldingelement (13) with image inversion.
 5. Optical auxiliary system accordingto claim 4 , characterised in that said front-surface reflector (11) isdisposed for rotation about an axis (12) orthogonally on the opticalaxis (10) of the system and is rotatable relative to said recording lens(1) in such a way that an oblique object plane (Bs) will be sharplyfocused onto said image plane (8).
 6. Optical auxiliary system accordingto claim 5 , characterised in that said path-folding element with imageinversion is a roof system (13).
 7. Optical auxiliary system accordingto any of the claims 3 to 6 , characterised in that an element (11) isrotatable together with said recording lens (1) in such a way that therespective pivoting angle of said recording lens corresponds to twicethe pivoting angle of said pivotable element.
 8. Optical auxiliarysystem according to claim 7 , characterised in that said pivotableelement is said front-surface reflector (11).
 9. Optical auxiliarysystem according to claim 8 , characterised in that a prism (14) isdisposed for image rotation between said first lens (3) and said secondlens (4).
 10. Optical auxiliary system according to claim 9 ,characterised in that said prism (14) is a Pechan-type or Dove-typeprism.
 11. Optical auxiliary system according to claim 10 ,characterised in that a gearing is provided which drives said prism insuch a way that the image position will not be varied.
 12. Opticalauxiliary system according to any of the claims 9 to 11 , characterisedin that said two lenses (4, 6), which are disposed between said prism(14) for image rotation and said zoom lens (7), present the sameconfiguration, and that said two lenses are disposed therebetween insymmetry relative to the centre plane.
 13. Optical auxiliary systemaccording to any of the claims 1 to 12 , characterised in that said zoomlens (7) is a varifocal lens.